JP2688024B2 - Insulated wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has good mechanical strength and flame retardancy used for wiring in equipment such as audio equipment and OA equipment, and has a low capacitance. It relates to insulated wires.

(Prior Art) FIG. 1 is a cross-sectional view of a general structure of a shielded wire,
(1) is a conductor, (2) is an insulating layer, (3) is a shield layer formed by winding a large number of tin-plated annealed copper wires on the insulating layer (2), and (4) is an external layer such as vinyl chloride. It is a coating layer.

Conventionally, a shielded electric wire using foamed polyethylene as the insulating layer (2) is used for signal transmission between television antennas and tuners, video signal transmission, audio signal transmission, computer interface transmission, etc. Widely used as electric wire.

FIG. 2 is a cross-sectional view of an example of a flat insulated wire. As shown in the drawing, a plurality of conductors (1) are arranged in parallel at intervals, and an insulating layer (2) is collectively formed on these conductors (1), for example. Layer (2)
Adjacent insulating layers (2) are connected to each other.

(Problems to be solved) However, in an electric wire in which the shield layer (3) is provided on the insulating layer (2) as shown in FIG. 1, electrostatic charges are generated between the inner conductor (1) and the shield layer (3). When a capacitance is generated and a high frequency signal is transmitted, the transmission loss becomes large. Therefore, it is essential to use a material having a small dielectric constant for the insulating layer (2) on the inner conductor (1) of these shielded wires. Foamed polyethylene has a cell ratio (total cell volume in material / total volume of material)
By changing the dielectric constant of the unfoamed 2.3
Therefore, it can be controlled to about 1.4 with a bubble ratio of 50%, and is suitable as an insulating layer (2) between the inner conductor (1) and the shield layer (3).

However, since polyethylene is flammable, fire spread prevention in the case of fire depends on the material of the highly flame-retardant outer coating layer (4) provided on the shield layer (3). Therefore, the safety of the terminal portion or the like from which the outer coating layer (4) has been removed is not sufficient, and the insulating layer (2) itself is required to have high flame retardancy.

Polyethylene is known to be highly flame-retardant by adding a halogen-based flame retardant and antimony oxide, but it is highly difficult to pass the UW-1 vertical burning test of UL standard. When imparted with flammability, the initial strength is significantly reduced. The initial strength required for the insulating layer is generally 1 kg / mm ² or more in tensile strength, but it is difficult to obtain this tensile strength with UW-1 level highly flame-retardant polyethylene with this dielectric constant of 2.0 or less. It was

Further, the flat insulated wire as shown in FIG. 2 is required to be downsized with the downsizing of audio equipment, OA equipment and the like.

When the flat insulated wire is downsized, the distance between conductors for transmitting digital signals becomes smaller. In such a flat insulated wire with a small distance between conductors, the capacitance of the capacitor formed by the adjacent conductors and the insulating layer sandwiched between the conductors becomes large, and the attenuation of the transmission signal is significantly large. Become. To prevent this, the dielectric constant (relative permittivity,
Hereinafter, a material having a small ε) may be used. Most of the conventionally used insulating materials are soft PVCs with ε of 4 or more, so if this is replaced with flame-retardant polyethylene with ε of about 3, the damping rate can be made slightly smaller. As an insulating material having a smaller ε than this, there is a fluororesin (ε2.1 to 2.5) such as polytetrafluoroethylene.

However, depending on the application, ε of the insulating material may be required to be 2 or less, and the conventional material cannot be used for this. As a method of reducing the ε of the material, it is known to make it porous by foaming, but when soft PVC or flame-retardant polyethylene is foamed until ε is 2 or less, the temperature drops remarkably and cannot be used as an insulating material. . Further, since foaming of a fluororesin has a very high processing temperature of 300 ° C. or higher, it is not easy to obtain a stable foam insulating layer.

(Means for Solving the Problem) The present invention provides an insulated wire which solves the above-mentioned problems, and its characteristic is that the elongation at break is 100% or more of the modified polyphenylene ether resin composition, and the decomposition temperature is 200. ~ 250
It is provided with an insulating layer foamed using a chemical foaming agent in the range of ° C.

(Function) The modified polyphenylene ether resin composition is generally known as a mixture of poly (2.6-dimethylphenylene ether) and polystyrene resin, or a grafter obtained by kraft-polymerizing styrene or the like on polyphenylene ether, to which a phosphate compound is added. It is commercially available as a flame-retardant additive. The ε of this flame-retardant modified polyphenylene ether is 2.7 or less, and in order to reduce ε to 2 or less, the porosity should be 34% or more. The initial tensile strength of the modified polyphenylene ether can because it is 3-4 kg / mm ^2, after foaming if Re performed uniform foam also is held sufficient 2 kg / mm ² approximately tensile strength as an insulating layer. On the other hand, soft PVC
Since ε is 4 or more, the porosity must be 60% or more in order to reduce ε to 2 or less, and the tensile strength after foaming is
It will be less than 1kg / mm ² . Also, since flame retardant polyethylene has an initial tensile strength of 1.5 kg / mm ² and ε of 3 to 3.5, when it is foamed so that ε is 2 or less, the porosity becomes 44% or more. The tensile strength after foaming is less than 1 kg / mm ² .

As the phosphate compound, cresyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, tricresyl phosphate, triisopropylphenyl phosphate, triphenyl phosphate, dibutylphenyl phosphate and the like can be used.

As a foaming agent, a foaming temperature such as p-toluenesulfonyl semicarbazide or azodicarbonamide is 200 to 2
50 ° C is preferable, and those that foam at a lower temperature than this do not form closed cells because the resin is not sufficiently melted, and when a high temperature foaming type is used, the melt viscosity of the modified polyphenylene ether resin becomes too low. Uniform foaming cannot be obtained.

As the method for forming the foamed insulation layer, a method in which the polyphenylene ether resin composition is extruded onto the conductor and simultaneously foamed, and a foaming agent is mixed with the polyphenylene ether resin at a foaming temperature or lower, and this is molded into an insulated wire at a foaming temperature or lower. After that, there is a method of heating the electric wire to a foaming temperature or higher for foaming. However, if the latter is heated and foamed after the insulated electric wire is formed, the porosity is not stable and the average bubble diameter becomes large, which is not preferable.

When performing foaming at the same time as extrusion, a method in which a foaming agent is mixed with a modified polyphenylene ether resin in advance at a foaming temperature or less, and a masterbatch in which a foaming agent is melt-mixed at a low temperature such as polyethylene and a modified polyphenylene ether resin are dispersed. There is a method of dry blending and extruding, but the former method of foaming and mixing with a modified polyphenylene ether resin cannot avoid some foaming during mixing. If bubbles are generated in this mixing stage, large bubbles causing pinholes in the insulating layer are not generated during foaming during subsequent extrusion, which is not preferable.

The method using the masterbatch of the foaming agent can completely prevent decomposition of the foaming agent by using a base polymer of the masterbatch that can be melt-mixed at 160 ° C. or lower. The polymer used in this masterbatch may be any that can be melt-mixed at 160 ° C or lower, such as polyethylene or ethylene-vinyl acetate copolymer,
Ethylene-α-olefin copolymers such as ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer and the like can be used.

(Example) Example 1: Modified polyphenylene ether resin containing about 30 parts by weight of a phosphate compound to 100 parts by weight of a resin component (tensile strength 3.
5kg / mm ² , elongation 150%, dielectric constant 2.6 / 1KHz) pellet 100
5 parts by weight of a master batch in which 30 parts by weight of p-toluenesulfonyl semicarbazide (decomposition temperature of 220 to 230 ° C) was dispersed in low density polyethylene was dry-blended with respect to parts by weight. A foamed electric wire was manufactured by extruding a 0.5 mm thick piece onto a conductor (0.5 mm diameter soft copper wire) at a set temperature of 230 ° C.

Uniform closed cells having an average diameter of 20 μm were formed in the coating layer of this electric wire, and no large bubbles having a diameter of 100 μm or more were observed. When the dielectric constant and tensile strength of this bubble layer were measured, the dielectric constant was 1.6 and the tensile strength was 1.8 kg / mm ² . The foamed electric wire was wound around a copper wire having a diameter of 1.5 mm and unwound, but no crack or buckling was observed in the coating layer. Furthermore, this wire passed the UL standard vertical burning test VW-1 and passed.

Example 2: A foamed electric wire was prepared in the same manner as in Example 1 except that azodicarbonamide was used as the foaming agent instead of p-toluenesulfonyl semicarbazide.

Uniform closed cells having an average diameter of 30 μm were also formed in the coating layer of this electric wire, and no large bubbles having a diameter of 100 μm or more were observed. When the dielectric constant and tensile strength of this foam layer were measured, the dielectric constant was 1.8 and the tensile strength was 1.6 kg / mm ² . Further, this foamed electric wire was wound around a copper wire having a diameter of 1.5 mm and unwound, but no crack or buckling was observed in the coating layer, and it passed VW-1.

Comparative Example 1: 100 parts by weight of low-density polyethylene (melt index 1) was mixed with 40 parts by weight of decabromodiphenyl ether, 30 parts by weight of antimony trioxide, 15 parts by weight of silica, 5 parts by weight of zinc oxide, and 1 part by weight of azodicarbonamide. A foamed electric wire was produced from the resin composition at a die temperature setting of 180 ° C. so as to have a dielectric constant of 1.6 as in Example 1.

In this case, there were no problems in the foamed state of the foam layer, winding, rewinding, and flame retardancy, but the tensile strength was 0.8 kg / mm ² , 1.0
It was less than kg / mm ² .

Comparative Example 2: Modified polyphenylene ether resin containing 15 parts by weight of a phosphate compound based on 100 parts by weight of a resin component (tensile strength 4.2 k
A foamed electric wire was manufactured in exactly the same manner as in Example 1 using g / mm ² , elongation of 60%, and dielectric constant of 2.5 / 1 KHz).

When the dielectric constant and tensile strength of this wire were measured,
The dielectric constant is 1.7 and the tensile strength is 2.1 kg / mm ² , which is good, and VW-1
Although it passed the test, when it was wound on a copper wire having a diameter of 1.5 mm, a crack was generated in the coating layer.

Example 3: Modified polyphenylene ether resin containing about 30 parts by weight of a phosphate compound based on 100 parts by weight of a resin component (tensile strength 3.
Disperse p-toluenesulfonyl semicarbazide (decomposition temperature 220-230 ° C) in low density polyethylene to 30% by weight per 100 parts by weight of pellets of 5 kg / mm ² , elongation 150%, ε2.6 / 1KHz). 5 parts by weight of the prepared masterbatch was dry blended, and this composition was extruded by an extruder at a die part set temperature of 230 ° C. to prepare a flat insulated wire having the structure shown in FIG. The conductor diameter of the flat insulated wire is 0.4 mmφ, the insulation thickness is 0.2 mm, and the conductor interval (P) is 1.0 mm.

In the insulating layer of this flat insulated wire, uniform closed cells having an average diameter of 20 μm were formed, and large bubbles having a diameter of 100 μm or more were not seen. The ε and tensile strength of this foamed insulation layer were measured and found to be 1.75 and 1.66 kg / mm ^{2 respectively.}
Met.

Example 4: A flat insulated wire similar to that of Example 3 was prepared by using azodicarbonamide instead of p-toluenesulfonyl semicarbazide as a foaming agent.

Uniform closed cells having an average diameter of 30 μm were also formed in the insulating layer of this flat insulated wire, and large bubbles having a diameter of 100 μm or more were not seen. The ε and tensile strength of this foamed insulating layer were measured and found to be 1.82 and 1.68 kg / mm ² , respectively.

Comparative Example 3: 100 parts by weight of low-density polyethylene (melt index 1) was mixed with 40 parts by weight of decabromodiphenyl ether, 30 parts by weight of antimony trioxide, 15 parts by weight of silica, 5 parts by weight of zinc oxide, and 1 part by weight of azodicarbonamide. Then, this was extruded at a die set temperature of 180 ° C., a flat type insulated wire was prepared so as to have the same ε as in Example 3, and its tensile strength was measured to be 0.78 kg / mm ² , which was 1 of Example 1. It was less than / 2.

Comparative Example 4: 50 parts by weight of dioctyl phthalate, 2 parts by weight of antimony trioxide, 5 parts by weight of tribasic lead sulfate, 10 parts by weight of clay, 2 parts by weight of azodicarbonamide, relative to 100 parts by weight of PVC resin (degree of polymerization: 1050). Was added to prepare a flat insulated wire with the same ε as in Example 3, and the tensile strength was measured to be 0.42 kg / mm ² , which was about 1/4 of that in Example 1.

The insulated wire of the present invention is not limited to the insulated wire having the structure shown in FIGS. 1 and 2, and for example, a plurality of wires of a wire having a shield layer on the outside of the insulating layer may be arranged in parallel. , A flat shielded electric wire having an outer coating layer common to them, or a plurality of wires of an electric wire having an insulating layer formed on a conductor are arranged in parallel, a common shield layer is provided on them, and an outer coating layer is provided thereon. Of course, it can also be applied to a flat shielded electric wire provided with.

(Effects of the Invention) As described above, according to the insulated wire of the present invention, the insulated wire is provided with the foamed insulating layer having high flame retardancy, excellent mechanical strength, and low dielectric constant. It is extremely effective when used as an electric wire for wiring.

[Brief description of the drawings]

FIG. 1 is a transverse sectional view of an example of a shielded electric wire, and FIG. 2 is a transverse sectional view of an example of a flat insulated electric wire. 1 ... Conductor, 2 ... Insulation layer, 3 ... Shield layer, 4 ...
Outer coating layer.

Claims (3)

(57) [Claims] 1. A modified polyphenylene ether resin composition having a breaking elongation of 100% or more, comprising an insulating layer formed by foaming with a chemical foaming agent having a decomposition temperature in the range of 200 to 250 ° C. Insulated wire to be used. 2. The insulated wire according to claim 1, wherein the modified polyphenylene ether resin composition contains a polyphenylene ether having a basic skeleton represented by the following structural formula and a phosphate compound. Here, R ₁ , R ₂ , R ₃ and R ₄ are monovalent substituents selected from hydrogen, alkyl groups, halogens, alkoxy groups and haloalkoxy groups, and n is a natural number. 3. A masterbatch in which a chemical foaming agent having a decomposition temperature in the range of 200 to 250 ° C. is dispersed in a resin having a mixing temperature of 150 ° C. or less, and a modified polyphenylene ether resin composition are formed on a conductor as an insulating layer. The insulated wire according to claim 1, which is formed by foaming at the same time as extrusion.